1. Field of the Invention
The invention relates to an imaging system and, more particularly, to a system for recording or reproducing a photographed image signal or input audio signal as a digital signal.
2. Related Background Art
Conventually, a digital electronic camera as shown in FIG. 1 typifies this type system.
In FIG. 1, reference numeral 800 denotes a digital electronic camera and 801 indicates a memory card which is used as its medium. In the digital electronic camera 800, reference numeral 1 denotes an image pickup lens; 2 a shutter having both of an iris function and a shutter function; 3 an electronic flash; 4 a CPU for controlling a mechanical and operation unit; and 5 a circuit for driving each unit of a mechanical system.
Reference numeral 6 denotes an image pickup element such as a CCD or the like for converting a reflected light from an object to be photographed to an electric signal; 7 a timing signal generation circuit (hereinafter, simply abbreviated as TG) for generating a timing signal that is necessary to make the image pickup element 6 operative; 8 an image pickup element driving circuit for amplifying a signal from the TG 7 to a level at which the image pickup element can be driven; 9 a preprocessing circuit having a CDS circuit to eliminate output noise of the image pickup element 6 and also having a nonlinear amplifying circuit to perform a nonlinear amplification before an A/D conversion; 10 an A/D converter; 12 a buffer memory; 13 a signal processing controlling CPU for controlling each signal processing unit; 14 an operation display unit for displaying messages for assisting an operation and a state of a camera; and 15 an operation unit to externally control the camera.
Reference numeral 802 denotes a memory controller for controlling the buffer memory 12; 803 a digital signal processing circuit for formatting an output of the image pickup element 6 to an output suitable for recording to the memory card 801; and 804 a memory card I/F (interface) to connect the digital electronic camera 800 and the memory card 801.
The operation will now be described.
First, by controlling the operation unit 15 by a photographer, the camera starts a photographing operation. In accordance with the operation by the photographer, a lens system is controlled by the mechanical and operation unit controlling CPU 4 and mechanical system driving circuit 5. In this instance, photographing conditions and the like are displayed on the operation display unit 14, thereby informing the state of the camera to the photographer. Further, a brightness of the object is measured by a photometric circuit (not shown) and an iris value and a shutter speed of the shutter 2 that is also used as an iris are calculated by the CPU 4. On the basis of a control value derived by the CPU 4, the shutter 2 is driven by the mechanical system driving circuit 5. In accordance with an output of the photometric circuit, the electronic flash 3 is turned on and the object is photographed.
The reflected light of the object which was exposed as mentioned above is inputted to the image pickup element 6 through the image pickup lens 1 and shutter 2. The shutter 2 limits an incident light amount to the image pickup element 6. In the case of using an interlace reading type CCD as an image pickup element 6, the shutter 2 is provided so that the incident light doesn't exert an adverse influence on signal charges during the transfer of the image signal. The image pickup element 6 is operated by a driving signal obtained by amplifying the output of the TG 7 by the image pickup element driving circuit 8. The operation of the TG 7 is controlled by the CPU 13.
The output of the image pickup element 6 driven as mentioned above is supplied to the preprocessing circuit 9. The preprocessing circuit 9 executes a CDS processing for eliminating low frequency noise included in the output of the image pickup element and a process for converting the image pickup signal to the nonlinear signal in order to effectively use a dynamic range of the A/D converter 10. The preprocessed image pickup signal is converted to a digital signal by the A/D converter 10 and is inputted to the memory controller 802.
Under control of the signal processing controlling CPU 13, the memory controller 802 first temporarily stores the digital image pickup signal into the buffer memory 12 and, further, reads out the image pickup signal in accordance with a predetermined order that is decided by a color filter construction or the like of the image pickup element 6. The read-out digital signal is converted to a signal of a predetermined format by the digital signal processing circuit 803 and is recorded in the memory card 801 through the memory card I/F 804.
The digital electronic camera as mentioned above, however, has the following problems.
(1) A function is limited to the image pickup recording of a still image and it is impossible to correspond the function to a moving image and to couple the image with audio data. PA1 (2) A data compressing method for efficiently recording data to a medium is limited and it is impossible to function with another method. PA1 (3) It is difficult to integrate an advanced information processing apparatus which can produce effective functions (functions such as optical character recognition, audio recognition, audio synthesis, translation, image recognition, image synthesis, etc.) by combining with the image pickup apparatus or an audio input/output device.
On the other hand, in order to solve the above problems, all of the processing functions must be built in the camera. The apparatus itself increases in size, as well as an extreme increase in price. Particularly, there is a problem such that those drawbacks become large disadvantages for the user who doesn't need such functions.
When such a moving image is recorded, for instance, a video camera of the NTSC system operates at a rate of 30 frames/second and it is impossible to change such a rate with control from the computer side. Therefore, even in the case where it is sufficient to use a low rate such as a few frames per second, the size of a recording file is large and a memory device of a large capacity is necessary for the computer side. In the case of a computer such that an image can be processed only at a low rate, an image signal cannot be outputted.